Journal ofCoastal Research 23-26 Fort Lauderdale, Florida Winter 1997

Evaluation of Sediment Transport Along the Nile Delta Coast, Egypt s. H. Sharar El Dint and A. M. Mahar:j:

Oceanography Department tEgyptian Navy Faculty of Science Hydrographic Department Alexandria University Ras El Tin Alexandria, Egypt Alexandria, Egypt ABSTRACT _

SHARAF, S. H. EL DIN and MAHAR, A.M., 1997. Evaluation ofsediment transport along the Nile Delta coast, Egypt. .tflllllll:. Journal of Coastal Research, 13(1), 23-26. Fort Lauderdale (Florida), ISSN 0749-0208. ~ Surface synoptic charts of the Eastern Mediterranean Sea have been used for a decade (1980-1989) to obtain data of euus wind direction and speed. Wind waves are predicted along the Nile Delta coast at five locations (Abu QuiI',Rashid, ~-~ Burullus, Ras El Bar and Port Said). The coastal array system (CAS) wave data obtained in 1988 are used to carry -+ a:= out a comparison between predicted and observed values of wave parameters at Abu Quir and Ras El Bar. It can be concluded that, the transport of sediment is eastward at Abu Quir, Burullus, Ras El Bar and Port Said. At Rashid the transport is mainly westward due to the effect of the NNE waves, while some reversal occurred. The transport is eastward when NNW and WNW waves dominate the area. The area between Abu QuiI'and Rashid and that between Ras El Bar and Port Said are characterized by accretion while those between Rashid and Burullus and between Burullus and Ras El Bar are characterized by erosion.

INTRODUCTION WAVE CliMATOLOGY The methods used to calculate the wave roses at the dif­ Waves which are invariant with time and governed mainly ferent stations along the Nile Delta coast is clearly illustrated by climate play a non negligible role in the manifestations by MAHAR (1993). Seasonal wave roses for Abu QuiI', Rashid, created on the Nile Delta coast. To estimate the amount of Burullus, Ras El Bar, and Port Said are given in Figure 2. sediment transport along the Nile Delta coast, it is important In winter season due to the rough weather the wave height to have some wave data close to the shore area of the study. of more than 2 m occur with 18.4%, 16.0%, 18.1%, 19.4% and Limitations in the available instrumentations led to incom­ 18.0% of the time at Abu Quir, Rashid, Burullus, Ras El Bar plete pattern of the wave field along the Nile Delta coast. For and Port Said, respectively. At Abu Quir and Port Said 70% that, mathematical model can be used to estimate the wind and 75% of the time, the waves are from NW/NNW sector, field and then the wave field at the required areas using the while at Burullus and Ras El Bar 80% of the time the waves synoptic weather charts of the eastern Mediterranean sea for are from NNW/N sector. At Rashid, 55% and 33% of the a decade (1980-1989) with two charts daily. The study of waves are from NNW/N sector and NNE sector respectively. wave growth in deep water is estimated. Inter-relationships The mean wave periods are 4.8 s with a maximum of 9 s between wave height, period, azimuth, water depth and or­ during that season. bital velocities lead to the calculation of the dissipation of In spring, the roughness of the weather decreases. The waves in shallow water due to the effect of bottom friction. wave heights of more than 2 m occur with 6.1%, 11.0%, 10.8%,11.9% and 6.1% of the time at Abu QuiI', Rashid, Bu­ Whence, coastal currents, littoral drift transport and the vol­ rullus, Ras El Bar and Port Said respectively. Wave angles umetric transport are calculated. are from the NW/NNW sector with 69% and 72% at Abu QuiI' The wave height, period and direction obtained from the and Port Said respectively, while at Burullus and Ras El Bar mathematical model at the five locations (Figure 1) are com­ 81% and 94% of the waves are from NNW/N sector respec­ pared with the actual field observations at Abu Quir and Ras tively. Finally, at Rashid 50.2% of the waves are from NNW El Bar. The correlation between predicted and observed wind sector and 38.7% are from NNE sector. The mean wave pe­ wave parameters indicate some variabilities. HASSELMANN riods are 4.4 s with a maximum of 7.6 s during that season. and COLLINS (1968) show that currents near bottom and also In summer, the wave height of more than 2 m occurs with vertical current shear would have a strong influence on the 3.3%, 4.3%, 4.3%, 2.5% and 2.7% at Abu QuiI', Rashid, Bu­ wave generation and hence on the wave parameters and this rullus, Ras El Bar and Port Said, respectively. Wave angles will lead to the variability between observed and predicted are 70% of the time from the NW/NNW sector at both Abu wave parameters. QuiI' and Port Said while they are 85% from NNW/N sector at Burullus and Ras El Bar and 68% from N/NNE sector at Rashid. The mean wave periods are 4.1 s with a maximum 94168 received 5 July 1994; accepted in revision 3 February 1996. of 7.7 s during that season. 24 Sharaf El Din and Mahar

3'l'-----' o KI1

MEDiTERRANEAN SEA

Ras el bar 3 \ ~o

Abu v ~,~) 0,00 30,)0 00 : I.l? 32,00

Figure 1. Chart showing the five locati ons at which wave par ameters were predi cted.

O~10 n ~ QD ~'"

. Winter season Spring season

O~10 ' .....

, io

Summer season Fall season Figure 2. Wave roses obtained along the coast of the Nile Delta during the four seasons (MAHAR, 1993).

Journal of Coastal Research , Vol. 13, No.1, 1997 Sediment Tr ansport Along the Nile Delt a 25

~ 1,00 ['-rriJ'-7d=.caCL- --, z 200nft day 0 >= w 100 0:: §~: U U a ~ 10~ I <{ _L_I. Ibl 100 100 z 200 6 200 o 300 if) 300 is o t5 400~~ --:-;-;---:-; ~ ---:- ---:----=~ ~~'--cJ t5 4 0 0'-'-~~~ ~~~~~~~ ,--'---Ll J FMAMJ JASO NDJ JF M A M J JA SO N 0 J ' ABU QUIR - RASHID RASHID- BURULLUS

m1 day Z 20 0 ,--'---'------, Q t;j 100 ~ ~ ~o~~ .... 100

2 00 z o if) 300 o 0:: W 4 0 0'-'-~~~~~~~~~~'--'--"-' FMAM JJA SOND RAS E L BAR - PORT SAID

Figure 3. Monthly mean budget of sediments for the coas tal sections along th e Nile Delta coast (MAHAR, 1993).

In autumn 8.0%, 4.2%, 6.2%, 6.8% and 7.5% of the wav e to ea st in the Mediterranean Sea (INMAN et al., 1975). The heights are more than 2 m at Abu Quir, Rashid, Burullus, migratory cyclones are cha nneled over the Mediterranean Ras EI Bar and Port Said, respectively. 50% of the waves are due to the eastward extention of the Azores high across North from NWINNW sector and 47% from NINNE sector at Abu Africa and th e westward extention of the Siberian high. Dur­ Quir and Port Said, 88% from NNWINNE sector at Rashid, ing spring, as the Siberi an high is displaced by the Asian while at Burullus and Ras EI Bar, 99% of the waves are from thermal depression over th e Eastern Mediterranean, the cy­ NNWINNE sector. The mean wave periods are 4.6 s with a clonic activity is weaken and the severity of sea decreases. In maximum of 9.3 s. summer, the Azores high and th e Asian low were completely The CAS (Coastal Array System) wave data of 1988 ar e dominating the climate and reach maximum inten sity caus­ used to compare between th e predicted and actual values of ing the frequency of severe seas to be at its minimum for the wave parameters at Abu Quir and Ras EI Bar. The compar­ year. Du ring autumn, th e Asian low and th e Azores high di­ ison is carried out using the hourly values, so th at there is minish in intensity as the Siberi an high becomes prominent no time lag between the compared pairs of data. Regression so th at a low pr essure trough with associated migratory cy­ analysis show th at the correlation coefficients are 0.887, clones is created in the Ea stern Mediterranean and th is caus­ -0.774,0.914 and 0.919 for wave heights at Abu Quir during es abrupt increase in the severity of the sea. winter, spring, summer and fall seas on respectively. For wave period, the values are 0.973 , 0.702, 0.934 , and 0.939 LONGSHORE SEDIMENT TRANSPORT respectively. Finally, they are - 0.936, 0.964 , -0.919 and 0.933 respectively for wave direction. Also at Ras EI Bar, th e Th e volum etric transport (Q) is given by KOMAR (1983) by corr elati on coefficients due to the regression analysis are Q, = (Ecn), vlUm -0.894,0.972, -0.982, and 0.755 for wave height during win­ ter, spring, summer , and fall seasons respectively. For wave where, E is the wave energy, c is th e phase velocity , n is ratio period the values are 0.908, 0.922, -0.886 and 0.942; whil e between group and phase velocity, v is th e littoral current for the wave directions they are 0.980 , 0.938 , 0.981 and 0.913 and Urn is th e maximum bottom horizontal orbital velocity respectively for th e same seasons. of th e waves evaluated at th e breaker zone. The variability of the wave's directions during win ter are The budget of each coastal section between two sequential due to the effect of the cyclonic storms which travel from west points is taken as th e difference between the input---output

Journal of Coasta l Research, Vol. 13, No. 1, 1997 26 Sharaf El Din and Mahar at the two bordering locations. The positive and negative bud­ Rashid, Burullus, Ras EI Bar and Port Said, respectively. The get of each section is a sign that indicates the variation of roughness of sea surface decreases to its minimum during the shoreline. summer so that 96.7,95.7,95.7,97.5 and 97.3 percent of the Due to the effect of the prevailing WNW and NNW waves waves had heights less than 2 m. at Abu Quir, NNW waves at Burullus, NNW and N waves at The transport is found to be eastward due to the effect of Ras EI Bar and W~'W and NNW waves at Port Said the WNW and NNW waves at Abu Quir, NNW waves at Burul­ transport is found to be eastward. At Rashid the transport is Ius, NNW and N waves at Ras El Bar and WNW and NNW mainly westward due to the effect of the predominant NNE at Port Said while at Rashid the transport is westward due waves. to the effect of NNE waves. A good correlation has been ob­ Figure 3 shows the monthly budget of the transported sed­ tained between the observed wave data of the CAS system iments for the coastal sections along the Nile Delta coast. The from Coastal Research Institute in Alexandria at Abu Quir method of estimating the sediment transport budget for each and Ras EI Bar, and that calculated hy MAHAR 11993) apply­ of the four sections is clearly indicated by MAHAR (1993). The ing mathematical model to synoptic charts. coastal section (Abu Quir-Rashid) is under the effect of ac­ The budget of the transported sediments along the Nile Del­ cretion all over the year with a maximum rate of 369 m'd 1 during December, while the coastal section (Rashid-c-Burul­ ta coast show that, the area between Abu Quir and Rashid Ius) is under the effect of erosion all over the year with a and that between Ras EI Bar and Port Said are characterized maximum rate of 342.3 m3d- 1 during December also. The by accretion while those between Rashid and Burullus and be­ coastal section (Burullus-s-Ras El Bar) is under the effect of tween Burullus and Ras EI Bar are characterized by erosion. accretion with a maximum of 108.7 m3d- 1 during April and under the effect of erosion during March, June, October and December with a maximum rate of 153.7 m3d-1 during De­ LITERATURE CITED cember. The coastal section (Ras El Bar-Port Said) is under HASSELMANN, K. and COLLINS, J.I.C., 1968.Spectral dissipation of 3d- 1 the effect of erosion with a maximum rate of 213.4 m finite depth gravity waves due to turbulent bottom friction. Jour­ during November except for the months January, October nal Marine Research, 26 (1). and December which are under the effect of accretion. INMAN, D.L.;AURBREY, D.G., and PAWKA, 8.8.,1975. Application of It has been found that, the area between Abu Quir and nearshore processes, to the Nile Delta. Proceedings October Sem­ Rashid and that between Ras EI Bar and Port Said are char­ inar on Nile Delta Shore Processes, UNESCO (Alexandria), pp. acterized by accretion; while the area between Rashid and 205-255. KOMAR, P.D., 1983. Nearshore currents and sand transport on Burullus and that between Burullus and Ras EI Bar are char­ beaches.In: JOHNS, B. (ed.), Physical Oceanography ofCoastal and acterized by erosion. Shelf Seas. Amsterdam: Elsevier, pp. 67-109. CONCLUSION MAHAR, A.M., 1993. Calculation of Waves from Synoptic Charts for Estimating the AmountofSediment Transport alongthe NileDelta During the winter season: 81.6%, 84.0%, 81.9%, 80.6% and Coast. Ph.D. thesis, Faculty of Science, Alexandria University, 82.0% of the waves had heights less than 2 m at Abu Quir, Egypt.

JournalofCoastal Research, Vol. 13, No. I, 1997